While I am pretty confident that Canon will have a new version of the 90 IS, I doubt that it will be 4 or 5 Mp because of the 10X lens. However, I have a D30, a 1V, and the 90 IS. I use an Epson 5500 printer. I sell my pictures (uo to 13x19) and have yet to have anyone comment that they were not taken with the same camera.
I use the 90 IS mostly for flowers and nature photography. It has the ability for keep the entire flower in focus vs. the 180mm L Macro. So for certain types of pictures it cannot be beat. One drawback is that the image cannot be manipulated as much in Photoshop.
It isn't only pixel count that makes a good digital camera. It is also the algorithms used and the quality of the firmware.
Roger